Since the Vietnam War, the M16 rifle family has been the primary rifle of the U.S. armed forces. The M16 is a family designation for several adaptations of this rifle to include the AR10®, AR-15, M16A1, M16A2, M4A1, M16A1 and the like and therefore being understood that the discussion herein includes this family of M16 style rifles but is not limited to it.
The family of M16 style rifles has undergone several modifications since it was first developed by Eugene Stoner and ArmaLite in 1954. Modifications include barrel length, barrel profile, rifling twist, barrel materials, hand-guard shapes, butt-stock types, grip types, lower receiver types, upper receiver types, rear sight types, rail systems, front sight types, muzzle devices, forward assist means, case deflectors, bayonet lug, trigger packs, and gas and piston operating systems. There have also been significant modifications to materials to reduce weight and improve component strength such as the use of polymers in butt-stocks, grips, and hand-guards. Modifications have basically improved the reliability and functionality of the M16 family of rifles without drastically changing the basic look and design of the original Stoner rifle. In the late 1950's the NATO 7.62×51 mm cartridge was introduced in U.S. service in the M14 rifle and M60 machine gun. The M14 was later superseded in the U.S. service as the infantry adopted the 5.56×45 mm NATO M16. Although the 7.62×51 NATO round was superseded by the later 5.56×51 NATO round, it is still in use in the M14 and other firearms as sniper rifles, machine guns and weapon of choice by special operation forces. M16 style rifles using the NATO 5.56×45 mm cartridge, or the M 193 cartridge designed by Winchester, later the Belgian 5.56 mm SS 109 cartridge was adopted as the standard by NATO due to its improved penetration design. Later, Colt developed the AR-15 models 601 and 602 which utilized the .223 caliber round. These two caliber rounds are still the primary rounds used in the M16 family of rifles by the military today with some variations in ammunition types.
One of the major problems with the M14 & M16 rifles is that they are limited in the size of caliber that can be used with a standard size bolt carrier and standard size butt assembly system. In order to increase the size of caliber beyond the NATO 5.56×45 round, the .223 caliber round, and the 7.62×51 mm NATO round, changes to the length of the bolt carrier, and size of the magazine well must also be proportionally increased to allow the bolt carrier assembly to eject a spent cartridge on the back stroke and insert a new cartridge from the magazine well into battery position on the return stroke. Lengthening of the bolt carrier would then necessitate that the butt assembly would also have to be extended to receive the longer bolt carrier when a round is fired. This creates two problems, first, it would require that a proprietary longer butt stock assembly be manufactured, and second, a larger butt stock assembly adds additional weight to the rifle. Both of these are unacceptable modifications for the military. U.S. Pat. No. 7,963,203 B1 makes use of a modified bolt carrier utilizing a weight element for timing purposes. U.S. Pat. No. 4,398,448 makes use of a buffered bolt assembly to reduce the load on the latch and cam pins during the firing cycle. Neither patent addresses modifications to the bolt carrier which extend the length of thereof to accommodate the use of other center fire cartridges within a standard butt assembly as claimed by the current invention.
It would be very advantages therefore, to remedy the foregoing deficiencies in the prior art to allow the use of larger caliber or long-action cartridges to be used with a standard OEM buffer assembly on an AR, M16, or M4 type platform, in particular for use as a sniper rifle for special operation forces, law enforcement, and for civilian use as a hunting rifle.
Accordingly, the present invention provides for a compressible bolt carrier extension that in a fully compressed state allows for a lengthened bolt carrier to function using long-action or other center fire cartridges within a standard OEM buffer assembly currently used with the M16 and M4 family of rifles.
A further object of the invention is to lessen felt recoil in the M16, AR, or M4 type rifle.